Comparative anatomy of the lower respiratory tract of the gray short-tailed opossum (Monodelphis domestica) and North American opossum (Didelphis virginiana)

by 1969- Cope, Lee Anne

Abstract (Summary)

The present study describes the lower respiratory tract anatomy of the gray shorttailed
opossum (Monodelphis domestica) and North American opossum (Didelphis
virginiana). The trachea of the gray short-tailed opossum consists of 25 c-shaped
tracheal cartilages. The trachea of the North American opossum consists of 28 c-shaped
cartilages. The right lung of both species is separated into cranial, middle, caudal and
accessory lobes by interlobar fissures. The left lung consists of unseparated cranial and
caudal lobes. The right and left pulmonary arteries of the gray short-tailed and North
American opossums divide into pulmonary lobar arteries. The pulmonary lobar veins
join to form pulmonary veins. In the gray short-tailed opossum, the pulmonary lobar
veins join to form a right and left pulmonary vein which join to form a common
pulmonary venous trunk. In the North American opossum, a similar pattern occurs
however the common pulmonary venous trunk is formed from three pulmonary veins
(right, left and middle). Vascularization of the lung parenchyma is via the bronchial
artery, a branch of the bronchoesophageal artery. Right and left bronchial branches
course along the dorsal surface of the principal bronchi toward the hilus of the lung. In
both species, the left bronchial branch anastomoses with a mediastinal artery originating
from the aorta. Cranial deep cervical, cranial mediastinal and tracheobronchial lymph
nodes drain the lower respiratory tract of both species. Sympathetic innervation to the
lungs of the opossums comes from the sympathetic trunks as thoracic splanchnic nerves.
Parasympathetic innervation to the lungs is via branches from the vagus nerves.
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The trachea and principal bronchi of the gray short-tailed opossum are lined by
pseudostratified ciliated columnar epithelium. Bronchial cartilages are irregular, shaped
plates and localized to the extrpulmonary portion of the principal bronchus. The
secondary and tertiary bronchi and primary and secondary bronchioles are lined by
simple ciliated columnar epithelium. The terminal bronchioles and proximal portion of
the respiratory bronchioles are lined by simple ciliated cuboidal epithelium. The distal
portion of the respiratory bronchioles and the alveolar ducts are lined by simple
squamous epithelium. The alveoli are lined by type I and II pneumocytes.
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